Morphological and¹³C-nuclear magnetic resonance studies for polyhydroxyalkanoate biosynthesis in<i>Pseudomonas</i>sp. 61-3

Abstract

Pseudomonas sp. 61-3 is able to produce a blend of poly(3-hydroxybutyrate) [P(3HB)] homopolymer and a random copolymer [P(3HB-co-3HA)] consisting of 3-hydroxyalkanoate units of 4–12 carbon atoms. In a cell accumulating polyhydroxyalkanoates upon glucose or alkanoic acids, both needle-type and mushroom-type structures were observed as PHA granules by freeze-fracture electron microscopy, indicating that Pseudomonas sp. 61-3 synthesized and stored both P(3HB) and P(3HB-co-3HA) granules simultaneously as separate granules in the same cell. 13C-NMR analysis of polyhydroxyalkanoates synthesized from 13C-labeled octanoate revealed that 3-hydroxybutyrate units in the resultant polyhydroxyalkanoates were not only supplied via fatty acid β-oxidation but also via dimerization of two acetyl-CoA molecules in Pseudomonas sp. 61-3. Approximately 26% of 3-hydroxybutyrate units was found to be generated via dimerization of acetyl-CoA when octanoate was fed as a carbon source.